why two hard links are created when a directory is created??

[pushparaj_bits]

helloo,

when I create a directory say mkdir newdir
and so stat newdir I get
stat newdir
File: `newdir'
Size: 4096 Blocks: 8 IO Block: 4096 directory
Device: 1dh/29d Inode: 19122900 Links: 2
Access: (0755/drwxr-xr-x) Uid: (52457/pushpara) Gid: ( 100/ users)
Access: 2009-10-21 13:44:25.062885000 +0000
Modify: 2009-10-21 13:44:25.062885000 +0000
Change: 2009-10-21 13:44:25.062885000 +0000

can any body explani why two hard links are created and what those are??

[William Haller]

One link is . which is the name of the current working directory.
One link is .. which is the name of the parent directory.

It's what lets you do ls -la ../someplace or ls -la ./thisplace and make it work without encoding the . and .. as special items in all the commands. Another way to think of it is the linkages from the root / of the tree down to where you are at.

[pushparaj_bits]

Hii william haller,

Thank you for your reply. What I understood is Hard links means number of different name pointing to the same physical file(block). So when we create a new directory with name newdir there are two different names pointing to the same newdir directory file. one is /root/.../newdir and other is . in the newdir . Also when we create a new directory say x in a directory y then the number of hard links to the directory y increses by 1.,because when we create new directory as you said .. will be created, which is pointing to the parent directory.

I am also getting an inference that there is limit to tht number of sub directories we can create in directory. Because the hardlink counter for the parent directory may be of 16 buts or 32 bits or 64 bits.

[William Haller]

There is a limit on the number of files or directories each directory can contain. This depends on the file system type. I suggest searching comparison of file systems in wikipedia and clicking on each possible file system type. This will have good information about limits of all sorts w.r.t. file systems.